What's everyone doin with these vent tubes? Keep / remove?
Pulled the LH kick panel out for the heater core replacement and found these. The ribbed flexible tube runs from somewhere in the plenum down to the rubber stack thing on the floor near the body mount.
Workshop manual is silent. Going to refit but wondering if anyone's run them out.
Owen - the ribbed tube is the heater plenum cold air bypass drain. The rubber stack on the floor is the corresponding sound-deadening rubber pillar that anchors it. KEEP both.
What the bypass drain does: when the heater is set to OFF or RECIRC, condensate inside the plenum is routed to drain harmlessly into the engine bay thru the rubber outlet under the car. If you delete the tube, water pools inside the plenum during humid weather and rots the inner floor pan from the inside out.
ive seen this exact deletion done by previous owners on three W108s in the last decade. All three had floor pan rot directly beneath where the tube should of drained. Cost approximately $1,200 to repair after the fact each time. Cost of keeping the tube: zero.
If yours are damaged, the rubber boot at the base (the "stack" you mentioned) is Mercedes-Benz part number 108 831 02 98, $38 from Mercedes-Benz Australia or $24 from Niemoeller. The ribbed tube is generic 32mm flexible PVC, $8/metre from any auto store, 800mm cut to length per side.
Refit. Don't delete.
I have.Billy is right.Also clean the inside of the ribbed tube before refit with a long brush and detergent.Mine had 50 years of dust and dried mud inside which was blocking the drain.Cleared it and the plenum stays dry now.westsydneyrestorationsbuilds.on facebook
Billy and Viktor - thank you both. Refit confirmed. Will clean the tubes through before they go back. Cheers..